Anhydrous metal fluoborates



Jan. 23, 1962 H. s. HALBEDEL ETAL 3,018,162

ANHYDROUS METAL FLUOBORATES Filed April 15. 1960 METAL BF, POLAR SOLVENTPLUORIDE soLu'noN REACT SEVERAL DAV-9 WITH 146/ TA 7'/0/V AND DEC/7N7 RESIDUE METAL FLUORIDE so LUTION PRODUCT A METAL an, 1 BFa soumou 1N pomsowam BFg TREATME/VTW/Tf/ COOLING; F/LTER mpuma METAL FILTRATE 3P4CRYSTALS f T WASH W/TH ETHER AND 3P SOLVENT PUMP DRV PRODUCT B METAL BF4CRYSTALS HAROLD S. HALBEDEL & WALTER B.FIELD, INVENTORS.

Eflldddd Patented Jan. 23, 1962 3,018,162 ANHYDRGUS METAL FLUOBQRATESHarold S. Halhedel, Euclid, and Walter B. Field, Cleveiand, @hio,assignors to The Harshaw Chemical Company, Cleveland, Chic, acorporation oft Uhio Filed Apr. i5, 196%), Ser. No. 22,447 6 Claims.(Ci. 23-59) This invention relates to anhydrous metal fluoborates and tothe methods of their preparation.

Metal fluoborates have found application as curing catalysts for variousresins, such as, for instance, epoxy resins, and for electroplating bathaddition agents. The curing of epoxy resins, however, frequently takesplace in a volatile organic solvent wherein the presence of water andparticularly the presence of water in the curing catalyst isundesirable. Fluoborates of lead, tin, cadmium, iron, indium, nickel andsilver are valuable salts in plating baths and are commonly sold insolution form as 50% concentration. The shipping and packaging of suchsolutions, however, is a major problem which could be eliminated by thepreparation of fluoborates in anhydrous form.

Most fluoborates as commonly prepared contain a certain amount of waterof hydration. The better known methods of preparation are: (a) thereaction of boron trifiucride with heated fluorides of certain metals;and (b) the reaction of fluoboric acid with a halide, oxide, hydroxide,carbonate, nitrate or sulfate of a metal. In general, fiuoborates ofgroup III-B meta-ls and the alkali metals, with the exception oflithium, are readily dehydrated by warming or the use of desiccants.Other fluoborates and more specifically the fluoborates of lithium,groups lI-B, II-B, III, IV-B, transition metals and alkaline earthmetals are strongly coupled to their waters of hydration. Variousattempts have been made to remove the strongly coupled Water ofhydration which is found in certain metal fluoborate crystals. When asimple application of heat is employed, it is found that thes metalfluoborate crystals lose water at about 40 C. to 60 C. However, themetal fluoborate is also subjected to a decomposition process whereinthere is a reversion to boron fluoride and metal fluoride. Attempts havealso been made to remove the water of hydration by an azeotropicdistillation process. The azeotropic distillation process employedbenzene as the immiscible liquid. The procedure did remove the bulk ofwater, but complete dehydration could not be effected. Continueddistillation merely resulted in decomposition of the meal fluoborate.

Metal fiuoborates which contain the ET, radical and liberate the BF; ionin solution should not be confused with metal fluoride-B19 complexes.Anhydrous metal fluoride-BT complexes may be formed by the addition of ametal fluoride to an ether-boron trifiuoride complex, followed byliberation of ether. Fluoborates in comparison with correspondinganhydrous metal fluoride-B1 complexes are generally superior for use ascuring catalysts or as salts in plating baths. The metal fluoride-BBcomplexes are unsuitable in that many of them break down at roomtemperature, liberating BF and also in that metal fluoride-BP complexesform metal fluorides when placed in water, the metal fluorides being ofno use in plating.

it is, therefore, an object of this invention to produce a method forthe preparation of anhydrous metal fluoborates.

it is a fiurther object of this invention to produce nonaqueous solvatedmetal fluoborates.

it is another object of this invention to produce a solution ofanhydrous metal fluoborate in an organic solvent.

We have now discovered that it is possible to produce anhydrous metalfluoborates by the addition of a metal fluoride to a solution of borontrifiuoride in an oxygen containing polar solvent which is not subjectto a breakdown, agitating the resultant solution, treating the solutionwith additional boron trifluoride, preferably diluted with small amountsof inert gas and recovering resultant anhydrous metal fluoboratecrystals. The anhydrous metal fluoborate crystals are found to becrystals of the solvated type, that is, their crystalline structure hasa polar solvent rather than water coupled therein.

If a solution of anhydrous meal fluoborate is desired, the aboveprocedure may be modified by elimination of the BF crystallizationaddition step. The resultant metal fluoborate solution may be packagedfor use as a resin curing catalyst.

A better understanding of the general type of applicants procedure maybe obtained from the accompanying flow sheet. The flow sheet shows theaddition of a metal fluoride to a B1 polar solvent solution. Theconcentration of BF may be in the range of from 5% to 50%; the pre--ferred range being from 15 to 40%. The resultant mixture is then reactedfor tWo or more days with agitation and then decanted. The residue whichis primarily metal fluoride or metal fluoride BF complex may be recycledto the B1 polar solvent solution. The resultant solution, which isdesignated on the flow sheet as Product A, may be drawn ed and packagedfor use as a resin curing agent. This product is particularly usefulwhere a slight excess of BF is not undesirable in the end use. As analternate to the packaging of the product at this point, the solutionwhich consists of a metal fluoborate in a BF polar solvent solution maybe drawn oil and the BF concentration slowly increased with cooling toabout 15% to 40% of B1 in polar solvent, the amount of 8P added beingthat which will produce maximum precipitation. The solution, thustreated, is then filtered. The filtrate from this operation with theaddition of BFg and polar solvent may be recycled to the initial BFpolar solvent solution. Crystals recovered from the filtration operationare impure metal fluoborate crystals which are washed with ether andpump dried to obtain purified metal fluoborate crystals, designated asProduct B on the flow sheet.

The reaction which takes place may be written as follows:

where M is a metal selected from the group consisting of lithium, li-B,11-13, Ill, IV-B, alkaline earth metals and transition metals, R is anoxygen containing polar solvent preferably selected from the groupconsisting of methanol and ethanol, and n is an integer equal to thevalence of the metal M.

The method of preparation of this invention is dependout upon thediscovery that fluobcrates result from the dissolution of metallicfluorides in coordination complexes of BF provided the bond strength ofthe solvent BF complex is less than the bond strength of the desiredfluoborate. To a degree this principle was recognized by the teachingsof the prior art. However, the only apparent use which was made of thisprinciple was to separate water or others from their respectivecomplexes with B1 in order to form metal fluoride-B1 complexes. Incontradistinction to this procedure, applicants invention is carried outby employing an organic complexing medium which is also a solvent forthe desired fluoborate. Applicants are therefore able to form, by meansof the controlled addition of BF a crystallized meallic compoundcontaining BF, radical.

The procedure of this invention necessitates a polar solvent which willnot break down to form dehydration products and which has some degree ofsolubility for the metal fluoborate formed. The term solvent as usedherein is synonymous with the term coordinating agent, that is, thesolvent for the metal fluoborate is also that compound which forms acoordination compound with BF Some 3: solvents which are suitable forthe purposes of this invention are methanol and ethanol, methanol beingpreferred because it is a better solvent for metal fluoborates. Specificexamples of the preparation of anhydrous metal fluoborates according tothis invention are as follows:

Example I 393 grams of BF were added to 690 grams of methanol in a2-liter three-neck flask over a 1 /2 hour period. An ice water bath wasused to take off the heat of reaction. One-half of the resultingsolution was placed in each of two l-liter Erlenmeyer flasks containing15 grams of Z11F2- The flasks were stoppered and placed on an Eberbachshaker. Alcohol was added after shaking one day to a total of 1090 gramsof alcohol (including original alcohol) for dissolution of zincfluoborate crystals and to enable good mixing. This was equivalent to a36% solution of BF (plus E las SP in alcohol. The solutions were allowedto settle 3 hours and the milky liquors decanted into a dry 2-literthree-neck flask in an ice water bath. 60 grams of alcohol insoluble Znlwere recovered from the flasks. A small flow of nitrogen was fed intothe flask and BF impinged slowly on the surface of the liquor whilestirring slowly. 150 grams of BB, were added over 1 /2 hours. Thisproduced an equivalent of 17% BE, in the BF -alcohol (alcohol tied up inthe solvated crystals included). The crystals were filtered on aBiichner funnel, washed with two 100 ml. portions of ether and pumpdried4 hours to very slight loss in weight. 57.3 grams of very hygroscopicsolvated zinc fluoborate crystals were obtained. A higher yield couldhave been obtained upon further addition of BF to about 25% BF in BF-alocohl. A large excess of BF however, was added to the liquor, thusdissolving the crystals.

Example II 100 grams of BaF and 232 grams of CH OH-BF solution (33.3% BFwere placed in a one-liter Erlenmeyer flask. 249 grams of CH O wereadded. The flask as stoppered and shaken for 3 days. The flask wasallowed to stand, the solution decanted into a one-liter three-neckflask in a cold water bath. BaF in the residue was 8.0 grams. 215 gramsof B1 diluted by a small flow of nitro gen were run in with mildagitation. A large crystalline precipitate was then filtered on aBiichner funnel. The BF addition was equivalent to 36% BF in BF-alcoho-l (alcohol tied up in solvated crystals included). 8P additionwas continued to a total of 310 grams (44% BE solution in alcohol onoriginal basis) for maximum precipitation. The salt was washed twicewith 100 ml. portion of anhydrous ether and pump-dried.

Example III 300 grams of zinc fluoride were reacted for two days with asolution of 393 grams of BF in 1179 grams of methanol (25% EE -methanolsolution) in two one-liter Erlenmeyer flasks. Constant agitation wasmaintained on an Eberbach shaker. The liquor Was decanted into atwo-liter three-neck flask in an ice water bath. 23 grams pf zincfluoride residue remained. 3P diluted by a small amount of nitrogen wasslowly added to 390 grams and 324 grams of crystals were filtered ofl.B1 addition was continued to 540 grams (total BR) and 611 grams ofcrystals separated. The total yield from above being 1001 grams of zincfluoborate crystals. The crystals were washed well with ether on aBlichner funnel and dried rapidly in a vacuum oven at 40 C. The crystalswere removed and packaged rapidly in glass jars with polyethyleneliners. Total Zn analysis 14.9% figured to Zn(BF is 54.4% by weight ofproduct. This agrees well with Zn(BF .6CH OH, theoretical Zn(BE 55.4%.

What we claim is:

1. A process for the preparation of anhydrous zinc fluoborate comprisingmixing Zinc fluoride with an anhydrous 25% solution of ER in methanol,agitating the mixture, removing unreacted metal fluoride, addingadditional BF diluted by a small flow of nitrogen and filtering offcrystals of anhydrous Zinc fluoborate.

2. A process for the preparation of an organic solution of anhydrouszine fluoborate comprising mixing zinc fluoride with an anhydrous 25%solution or 131 and methanol, agitating the mixture and removingunreacted metal fluoride.

3. A process for the preparation of anhydrous barium fluoboratecomprising mixing barium fluoride with an anhydrous 33.3 solution of BB,in methanol, agitating with additional methanol, removing unreactedmetal fluoride, adding additional B1 and filtering oil crystals ofanhydrous barium fluoborate.

4. A process for the preparation of a solution of anhydrous bariumfluoborate in an anhydrous organic solvent comprising mixing bariumfluoride with a 33.3% solution of BF in methanol, agitating withadditional methanol, and removing unreacted metal fluoride.

5. A process for the preparation of an anhydrous metal fiuoboratecomprising mixing a metal fluoride selected from the group consisting ofZinc fluoride and barium fluoride with a 5% to 50% solution of BF in ananhydrous oxygen containing polar solvent, agitating the mixture,removing unreacted meal fluoride, adding additional BF and filtering oflcrystals of anhydrous metal fluoborate.

6. A process for the preparation of a solution of anhydrous metalfluoborate comprising mixing a metal fluorideselected from the group ofzinc fluoride and barium fluoride with a 5% to 50% solution of BF in ananhydrous oxygen containing polar solvent, agitating the mixture andremoving unreacted metal fluoride.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES I. W. Mellors A Comprehensive Treatise on Inorg. andTheoretical Chemistry, vol. 5, 1924 Ed., page 123, Longmans, Green andCo., NY.

Great Britain June 10, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No 3,018,,162 January 23 1962 Harold S, Halbedel etal.,

It is" nerebyoeroifmd that error appears in ,the above numberedpatentrequiring correction andbhat the said Letters Patent should readas "corrected below.

Column 2, line 63 for "meallic" read metallic:

column 3 line 32", "-alocohl" read alcohol line 40 for "CH O" read --.CHOH column 4 line ll for "meal" read metal Signed and Sealed this 8th dayof May 1962;.

(SEAL) Attest:

ERNEST W. WIDE Attesting Officer DAVID L. LADD Commissioner of Patents

5. A PROCESS FOR THE PREPARAING OF AN ANHYDROUS METAL FLUOBORATECOMPRISING MIXING A METAL FLUORIDE SELECTED